Avalanche Forecast
Issued: Feb 21st, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Cornices and Persistent Slabs.
zryan,
Avalanche Canada
Continue to make conservative terrain choices as the recent storm snow may bond poorly to the underlying hard surface.
Watch for fresh wind slabs forming as northerly outflow winds cross- and reverse-load atypical terrain features.
Summary
Confidence
Weather Forecast
Bundle up in your warmest gear, arctic air is here!
Monday Overnight: Clear skies. Alpine temperatures around -25 C. Light to moderate northeasterly winds.
Tuesday: Cold and clear. An alpine high of -20 C. Light northeasterly winds.
Wednesday: Mainly cloudy with light snowfall. Winds shifting northwest and strengthening moderate to strong. Alpine temperatures rising to -15 C.
Thursday: Partially cloudy. Light to moderate northwest winds. Alpine temperatures around -15 C.
Avalanche Summary
Sunday was an active day for avalanche activity! Numerous human-triggered storm slabs and wind slabs were reported mainly in the alpine and treeline, with many of these avalanches failing on the mid-February drought layer. Several natural wind slab, storm slab, and dry loose avalanches occurred, some as a result of cornice failures.
In the north of the region, a natural avalanche cycle likely occurred during the peak of the storm on Saturday afternoon. Numerous human-triggered storm and wind slabs were reported throughout the day. In the south of the region, wind slabs were reactive to human triggering, with natural loose dry avalanches observed out of steep terrain in the alpine.
Explosive control last week initiated some larger persistent slabs up to size 3 on north-facing aspects at treeline.
Snowpack Summary
Last weekend's storm brought 20-80 cm of new snow accompanied by southwesterly winds. The north of the region received highest snowfall amounts, with tapering amounts to the south. Below ~1200 m the majority of the precipitation fell as rain, with 10-20 cm of snow now overlying a thick melt-freeze crust.
Up to 120 cm now overlies the mid-February drought layer. This layer is comprised of surface hoar in sheltered areas, a melt-freeze crust at lower elevations, a sun-crust on steep solar aspects, and hard wind-affected snow in the alpine and exposed treeline. In many areas, the storm snow is bonding poorly to this firm layer.
The mid-January surface hoar/crust layer is now down 50-150 cm in the snowpack. This layer has not been reactive to skier traffic in the past week but continues to show reactivity in snowpack tests. With a significant amount of new snow, this layer could start to 'wake up' or be triggered from a large load like a cornice fall or a shallower slab avalanche stepping down to this layer.
The facet/crust layer that formed in early December is now buried around 150 to 250 cm. Human triggering of this layer is unlikely, except perhaps on a re-loaded bed surface or in a shallow snowpack area. This layer may become a concern during periods of warming or heavy loading.
Terrain and Travel
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Use small low consequence slopes to test the bond of the new snow.
- Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
Problems
Storm Slabs
This weekend's storm brought 30-100 cm of storm snow overlying the February 15th drought layer. Reports suggest that the storm snow is bonding poorly to this interface and human-triggering could persist into Tuesday.
The highest snowfall amounts were reported in the north of the region. A more widespread storm slab problem could still exist, but expect to find deeper, and stiffer slabs to exist in wind-loaded terrain. In the south of the region, the problem is more likely confined to a wind slab problem in lee areas.
Northeasterly outflow winds may have created wind-loaded pockets in more atypical, reverse-loading patterns and at lower elevations than you might usually expect.
Dry-loose avalanches may be seen from steeper slopes, especially where a firm crust exists below the new snow.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Cornices may have grown significantly with wind and snowfall over the past 3 days. Be especially mindful of overhead cornice hazard if the sun comes out and the storm snow is experiencing strong solar radiation for the first time.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer formed in late January may be found 50 to 150 cm deep in the snowpack. This layer consists of faceted snow, a sun crust on steep solar aspect, and most notably large surface hoar crystals in sheltered terrain.
Reactivity on this layer has tapered, but the significant amount of new load over the weekend may cause this layer to 'wake up'.
The most reactivity on this layer has been seen between 1600-2200 m in open areas in the trees, in cut blocks, and on steep convexities. Terrain features to be suspect of include the lee side of ridges, openings in trees, cut blocks, and burns, especially on northerly aspects where the layer may not be capped by a firm crust.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 22nd, 2022 4:00PM
